# Standard library header <new>

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< cpp‎ | header

This header is part of the dynamic memory management library, in particular provides low level memory management features.

### Classes
bad_alloc | exception thrown when memory allocation fails (class)
bad_array_new_length (C++11) | exception thrown on allocation of array with invalid length (class)
align_val_t (C++17) | type used to pass alignment to alignment-aware allocation and deallocation functions (enum)
### Types
new_handler | function pointer type of the new handler (typedef)
### Tags
nothrownothrow_t | a tag used to select a non-throwing allocation function (tag)
destroying_deletedestroying_delete_t (C++20) | a tag used to select destroying-delete overloads of operator delete (tag)
### Constants
hardware_destructive_interference_sizehardware_constructive_interference_size (C++17) | min offset to avoid false sharing max offset to promote true sharing (constant)
### Functions
operator newoperator new[] | allocation functions (function)
operator deleteoperator delete[] | deallocation functions (function)
get_new_handler (C++11) | obtains the current new handler (function)
set_new_handler | registers a new handler (function)
launder (C++17) | pointer optimization barrier (function template)

### Synopsis

    namespace std {
      // storage allocation errors
      class bad_alloc;
      class bad_array_new_length;

      struct destroying_delete_t {
        explicit destroying_delete_t() = default;
      };
      inline constexpr destroying_delete_t destroying_delete{};

      // global operator new control
      enum class align_val_t : size_t {};

      struct nothrow_t { explicit nothrow_t() = default; };
      extern const nothrow_t nothrow;

      using new_handler = void (*)();
      new_handler get_new_handler() noexcept;
      new_handler set_new_handler(new_handler new_p) noexcept;

      // pointer optimization barrier
      template<class T> constexpr T* launder(T* p) noexcept;

      // hardware interference size
      inline constexpr size_t hardware_destructive_interference_size =
        /* implementation-defined */;
      inline constexpr size_t hardware_constructive_interference_size =
        /* implementation-defined */;
    }

    // storage allocation and deallocation
    void* operator new(std::size_t size);
    void* operator new(std::size_t size, std::align_val_t alignment);
    void* operator new(std::size_t size, const std::nothrow_t&) noexcept;
    void* operator new(std::size_t size, std::align_val_t alignment,
                                     const std::nothrow_t&) noexcept;

    void  operator delete(void* ptr) noexcept;
    void  operator delete(void* ptr, std::size_t size) noexcept;
    void  operator delete(void* ptr, std::align_val_t alignment) noexcept;
    void  operator delete(void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
    void  operator delete(void* ptr, const std::nothrow_t&) noexcept;
    void  operator delete(void* ptr, std::align_val_t alignment,
                          const std::nothrow_t&) noexcept;

    void* operator new[](std::size_t size);
    void* operator new[](std::size_t size, std::align_val_t alignment);
    void* operator new[](std::size_t size, const std::nothrow_t&) noexcept;
    void* operator new[](std::size_t size, std::align_val_t alignment,
                                       const std::nothrow_t&) noexcept;

    void  operator delete[](void* ptr) noexcept;
    void  operator delete[](void* ptr, std::size_t size) noexcept;
    void  operator delete[](void* ptr, std::align_val_t alignment) noexcept;
    void  operator delete[](void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
    void  operator delete[](void* ptr, const std::nothrow_t&) noexcept;
    void  operator delete[](void* ptr, std::align_val_t alignment,
                            const std::nothrow_t&) noexcept;

    constexpr void* operator new  (std::size_t size, void* ptr) noexcept;
    constexpr void* operator new[](std::size_t size, void* ptr) noexcept;
    void  operator delete  (void* ptr, void*) noexcept;
    void  operator delete[](void* ptr, void*) noexcept;

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